JP3312252B2 - Exhaust valve device for two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust valve device for a two-cycle engine having an exhaust valve facing an exhaust port.

[0002]

2. Description of the Related Art Conventionally, this type of exhaust valve device includes a main exhaust passage communicating with a main exhaust port of an engine cylinder and an auxiliary exhaust passage communicating with auxiliary exhaust ports on both sides of the main exhaust port. There is a type in which valves are provided, and the cross-sectional area of the entire exhaust passage is changed by these valves (for example, see JP-A-63-173817).

In the conventional exhaust valve device disclosed in this publication, when the engine is rotating at a low speed, both valves are closed to reduce the cross-sectional area of the exhaust passage, and the two valves are switched as the engine speed increases. It had an open structure.

The main exhaust valve provided in the main exhaust passage has a structure in which a substantially plate-shaped valve body is supported so as to be vertically swingable above the main exhaust passage, and an end portion thereof faces the main exhaust port. As the auxiliary exhaust valve provided in the auxiliary exhaust passage, a rotary valve that rotates with respect to the cylinder has been used. In addition, the main exhaust valve and the sub exhaust valve are configured to open simultaneously.

That is, in the conventional exhaust valve device, the cross-sectional area of the exhaust passage is small when the engine is rotating at a low speed, and increases as the engine speed increases. For this reason, an exhaust passage cross-sectional area commensurate with the engine speed can be obtained, and high output can be obtained over the entire rotation range.

[0006]

However, even if the auxiliary exhaust passage is provided on the side of the main exhaust passage so as to change the cross-sectional area of the exhaust passage to a size corresponding to the engine speed, it is not always necessary to perform the full rotation. No high power was obtained over the region. This is considered to be related to the exhaust timing when the auxiliary exhaust valve opens as described below.

When the engine speed is in a low speed range, the exhaust timing has a large effect on the engine output. Therefore, it is important to accurately control the exhaust timing at that time in order to obtain a high output.

However, in the above-described conventional exhaust valve device, when the sub-exhaust valve is opened, the engine is operated in spite of the fact that the main exhaust valve is located at a position where the exhaust timing adapted to the medium speed rotation is obtained. The actual exhaust timing is rapidly accelerated, and the exhaust timing control becomes inaccurate. This is because, when the auxiliary exhaust valve is opened, even if the opening degree is small, the actual exhaust timing of the engine is when the piston passes the upper edge of the auxiliary exhaust port.

That is, if the main exhaust valve and the sub-exhaust valve are simultaneously opened when the engine speed increases from the low speed range to the middle speed range, the exhaust timing will be unnecessarily advanced, and the engine output Is easily reduced.

[0010]

An exhaust valve device for a two-stroke engine according to the present invention is disposed at a central portion of a main exhaust passage, faces a main exhaust port, and has a protruding amount changed according to the engine speed. A sliding main exhaust valve for changing the exhaust timing, a pair of sliding auxiliary exhaust valves facing the auxiliary exhaust port on the side of the main exhaust port and changing the passage cross-sectional area, and one exhaust valve for driving both exhaust valves A drive mechanism, wherein the exhaust valve mechanism has a structure having an idle stroke in which only the main exhaust valve opens and closes, and an interlocking stroke in which both the exhaust valves open and close integrally, wherein the engine speed is smaller than a set speed. Sometimes, the valves are fully closed and the main exhaust valve is opened when the set number of revolutions is exceeded,
Thereafter, when the engine speed increases by a certain value, the sub exhaust valve is opened integrally with the main exhaust valve.

[0011]

Since the main exhaust valve opens before the auxiliary exhaust valve opens, the exhaust timing of the engine is controlled by the main exhaust valve when the engine speed increases from a low speed range to a medium speed range. Also, compared to a structure in which the main exhaust valve and sub-exhaust valve are individually opened and closed by a dedicated drive mechanism, an interlocking mechanism that connects the respective drive devices and interlocks the opening and closing timing of both the main and sub-exhaust valves, etc. Not required.
Since the opening and closing timing and opening of each of the two exhaust valves can be determined by one exhaust valve drive mechanism,
Opening and closing control for opening and closing the two exhaust valves in association with each other can be easily performed.

[0012]

FIG. 1 to FIG. 12 show an embodiment of the present invention.
This will be described in detail. 1 is a cross-sectional view of a two-stroke engine equipped with an exhaust valve device according to the present invention, FIG. 2 is an enlarged cross-sectional view showing a main exhaust valve driving section of the exhaust valve device according to the present invention, and FIG. FIG. 4 is a cross-sectional view taken along the line III-III, FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 1, and FIG. 5 is a cross-sectional view showing, in an enlarged manner, a sub-exhaust valve driving unit of the exhaust valve device according to the present invention. FIG. 5 is a sectional view taken along line VV in FIG. FIG. 6 is a sectional view of the main exhaust valve, and FIG. 7 is a view taken in the direction of arrow A in FIG. 1 with a cover removed.

FIG. 8 is an exploded perspective view of the exhaust valve driving mechanism.
9A and 9B are cross-sectional views for explaining the operation of the main exhaust valve for the high-speed range. FIG. 9A shows a fully closed state, FIG. 9B shows a state when it starts to open, and FIG. ) Indicates a fully open state.

FIGS. 10A and 10B are cross-sectional views for explaining the operation of the sub-exhaust valve. FIG. 10A shows a fully closed state, FIG. ) Shows a fully opened state, and FIG. 4D shows a state when the low-speed main exhaust valve and the high-speed main exhaust valve are fully opened. FIG. 11 is a graph showing the relationship between the engine speed and the valve stroke amount of the exhaust valve device according to the present invention.
2 is a graph showing the change in exhaust timing, and FIG. 13 is a graph showing the relationship between the engine speed and the output of the engine equipped with the exhaust valve device according to the present invention.

In these figures, reference numeral 1 denotes a motorcycle 2
In the cycle engine, a cylinder body 3 is mounted on a crankcase 2 of the engine 1, a cylinder head 4 is further mounted on the cylinder body 3, and an ignition plug 5 is provided on the cylinder head 4.

A piston 6 is slidably provided in the cylinder of the cylinder body 3, and the piston 6 is connected to a crank arm 9 of a crank shaft 8 via a connecting rod 7. The crank arm 9 is housed in a crank chamber 10 of the crank case 2.
Reference numeral 0 denotes a scavenging port 11a which is opened in the middle of the cylinder body 3 through a scavenging passage 11 formed in the cylinder body 3.
Is in communication with

An intake passage 12 communicating with the crank chamber 10 is formed in the cylinder body 3 below the scavenging port 11a, and a main exhaust passage communicating with the inside of the cylinder of the cylinder body 3 is provided at a position facing the intake passage 12. The main exhaust passage 13 and the inside of the cylinder of the cylinder body 3 communicate with each other through auxiliary exhaust passages 14 located on both sides of the main exhaust passage 13.

The upper side of the main exhaust passage 13 (the cylinder head 4
The main exhaust valve 15 for the low-speed range and the main exhaust valve 16 for the high-speed range for varying the exhaust timing and the cross-sectional area of the main exhaust passage according to the engine speed are provided in the valve mounting hole 3a formed on the cylinder side. They are mounted in a state where they are arranged along the axial direction.

The high-speed main exhaust valve 16 of the two main exhaust valves is disposed so as to face a portion of the cylinder opening 13a of the main exhaust passage 13 on the cylinder head 4 side. The exhaust valve 15 is disposed at a position below (on the crankshaft side) the main exhaust valve 16 for the high-speed range. In addition, these main exhaust valves 1
As shown in FIG. 3, 5 and 16 are disposed at a central portion in the lateral direction so as to extend from one side of the main exhaust passage 13 to the other side thereof, and contact and separate from the upstream end of the main exhaust passage 13. It adopts a structure that slides as if to slide.

As shown in FIG. 8, the low-speed main exhaust valve 15 comprises a substantially plate-shaped valve element 15a and a rod-shaped valve shaft 15b. It is supported by an exhaust valve 16. And the valve shaft 1
A pin 15c erected on 5b is connected to an exhaust valve driving mechanism described later.

The end (end 15d) of the valve body 15a on the exhaust passage side is formed in a shape conforming to the shape of the main exhaust passage 13.

As shown in FIG. 8, the high-speed main exhaust valve 16 has a valve body 16a formed in a substantially plate shape, a valve guide 16b inserted into a valve mounting hole 3a of the cylinder body 3, and a valve guide 16b. And an operation block 17 screwed to the valve guide 16b. In addition, valve element 1
The end of the exhaust passage 6a (tip 16c) on the exhaust passage side is formed in a shape conforming to the shape of the main exhaust passage 13 in the same manner as the low-speed main exhaust valve 15. The operation block 17 is connected to an exhaust valve driving mechanism described later.

Further, the valve guide 16b and the operation block 17 are formed with through holes for supporting the valve shaft 15b of the low speed main exhaust valve 15 so as to be able to move forward and backward.

The operation block 17 is fixed to the valve guide 16b by a mounting screw 17a.
7b and a connecting portion 17 formed integrally with the main body 17b.
c.

As shown in FIG. 2, the lower portion of the connecting portion 17c has two upper and lower arcuate surfaces 17d and 17e, and a projection 1 which opposes an end of the upper arcuate portion through a notch 17f.
7 g are formed.

The main exhaust valve 15 for the low speed region and the main exhaust valve 16 for the high speed region thus configured are connected to the main exhaust passage 13.
, The exhaust timing and the cross-sectional area of the main exhaust passage 13 can be changed.

Further, as shown in this embodiment, by forming the valve bodies 15a and 16a of these main exhaust valves 15 and 16 in a plate shape, the exhaust timing and the passage in the main exhaust passage 13 having a large cross-sectional area are provided. The cross-sectional area can be easily changed.

Above the auxiliary exhaust passage 14, a columnar slide type auxiliary exhaust valve 18 is provided in the auxiliary exhaust passage 14 in the direction of the cylinder opening 14a in the same manner as the low and high speed main exhaust valves 15, 16. The auxiliary exhaust passage 1 is provided so as to be capable of moving back and forth.
The cross-sectional area of the passage 4 is variable.

As shown in FIG. 8, the sub exhaust valve 18 has a columnar valve body 18a, a valve shaft 18b formed integrally with the valve body 18a, and a sub exhaust valve screwed to the valve shaft 18b. A valve operating block 19, and a valve shaft 18b.
Are supported on the cylinder body 3 by a valve guide 18c so as to be able to advance and retreat.

The sub-exhaust valve 18 is connected to an exhaust valve driving mechanism, which will be described later, via a sub-exhaust valve operating block 19, and is configured to open and close at a predetermined timing in accordance with the engine speed. ing.

By forming the sub-exhaust valve 18 in a columnar shape and making the cross section of the tip 18d substantially coincide with the cross section of the passage, the valve itself can be easily formed.
The valve hole machining is easy, and the influence on the strength of the partition wall 20 between the auxiliary exhaust passage 14 and the main exhaust passage 13 is reduced.

The operating block 19 for the auxiliary exhaust valve includes:
As shown in FIG. 8, a mounting screw 19a is attached to the valve shaft 18b.
The main body 19b is attached to the main body 19b, and the main body 19b has an open-side projection 19c and a closed-side projection 19d. 5 is provided on the lower surface of the closed side projection 19d.
As shown in FIG. 10, an arc surface 19e is formed.

The low-speed main exhaust valve 15, the high-speed main exhaust valve 16 and the sub exhaust valve 18 are driven by one exhaust valve driving mechanism 21.

The exhaust valve drive mechanism 21 is formed as shown in FIG. 8, and the rotation angle of one shaft 22 is changed in accordance with the engine speed to achieve the above-mentioned operation.
The kind of exhaust valve is configured to be opened at a predetermined timing.

The shaft 22 is disposed in a direction perpendicular to the cylinder axis, and is provided with a pin 1 of the low speed range main exhaust valve 15.
The drive fork 23 with which the 5c is engaged, the drive block 24 connected with the operation block 17 of the main exhaust valve 16 for the high-speed range, the drive plate 25 connected with the operation block 19 for the sub-exhaust valve, and the like are fixed. .

A driving device (not shown) for changing the rotation angle of the shaft 22 according to the engine speed is connected to the shaft end of the shaft 22.

The drive fork 23 is formed with a groove 23a into which the pin 15c of the low-speed main exhaust valve 15 is fitted. It is configured to advance and retreat.

The drive block 24 includes a pressing portion 24a which contacts the projection 17g of the operation block 17, and a fan-shaped portion 24 which slides on the lower circular surface 17e of the operation block 17.
and b are formed integrally. The pressing portion 24a is
The tip surface is an arc surface that slides on the upper arc surface 17 d of the operation block 17. The outer peripheral surface of the fan-shaped portion 24b is an arc surface having a curvature substantially equal to that of the arc surface 17e.

The driving plate 25 is formed in a narrow fan shape.
Both protrusions 19c of the sub exhaust valve operating block 19,
A pressing portion 25a that engages between 19d is formed. The center of the circular arc forming the outer peripheral edge of the pressing portion 25a is the same as the rotation center of the shaft 19, and the circular arc has the same curvature as the circular arc surface 19e formed on the lower surface of the closed side projection 19d. Are formed to be substantially equal.

According to the exhaust valve driving mechanism 21 configured as described above, by rotating the shaft 22, the low-speed main exhaust valve 15, the high-speed main exhaust valve 16 and the sub exhaust valve 18 are interlocked. To go back and forth.

The low speed main exhaust valve 15 is
The main exhaust valve 16 and the auxiliary exhaust valve 18 for the high-speed range are operated by the operation block 17 and the drive block 24, and the operation block 1 for the auxiliary exhaust valve.
The main exhaust valve 15 for the low speed range is sequentially opened and closed in a state of being opened by a predetermined opening degree by the time difference drive structure by the drive plate 9 and the drive plate 25.

The drive system of the high-speed main exhaust valve 16 is configured such that the opening change amount (valve stroke amount) with respect to the rotation amount of the shaft 22 is substantially equal to that of the low-speed main exhaust valve 15. I have. That is, when the high-speed main exhaust valve 16 opens and closes, the high-speed main exhaust valve 16 and the low-speed main exhaust valve 15 open and close with the same amount.

In FIGS. 1 and 2, reference numeral 26 denotes a cover which is housed so as to cover the exhaust valve driving mechanism 21, and is fixed to the cylinder body 3 of the engine 1.

Next, the operation of the three types of exhaust valves will be described with reference to FIGS. 9 (a) to 9 (c) and 10 (a) to 10 (d).

When the engine speed is in the low speed range below the set speed, the shaft 22 of the exhaust valve drive mechanism 21 is rotated right in FIG.
The high-speed main exhaust valve 16 and the sub exhaust valve 18 are fully closed. FIG. 9A shows a fully closed state of the main exhaust valve 16 for the high-speed range, and FIG.
(A).

At this time, the low speed range main exhaust valve 15
Is advanced to the cylinder opening 13a side of the main exhaust passage 13 by the driving fork 23 of the shaft 22. The pressing portion 24a of the driving block 24 for driving the high-speed main exhaust valve 16 has a circular arc surface at the tip thereof.
7 is in contact with the arc surface 17d. Further, the outer peripheral surface of the pressing portion 25a of the driving plate 25 for driving the sub-exhaust valve 18 is in contact with the arc surface 19e of the sub-exhaust valve operating block 19.

The exhaust timing of the engine 1 at this time is set relatively late so as to be suitable for low-speed operation. The position of the tip of each exhaust valve when fully closed is indicated by a two-dot chain line a in FIGS. 2 and 5. Sub exhaust valve 18 shown in FIG.
The fully closed position is such that the distal end portion 18d of the auxiliary exhaust valve 18 is slightly separated from the bottom wall of the auxiliary exhaust passage 14, but the auxiliary exhaust passage is Since the state is equivalent to the fully closed state, there is no problem in operation and effect. In the present embodiment, the position of the auxiliary exhaust valve 18 when the auxiliary exhaust passage 14 is substantially fully closed as described above is simply referred to as the fully closed position.

When the engine speed exceeds the set speed and the engine rotates at a medium speed, the shaft 22 is rotated counterclockwise in FIG. At this time, the low-speed main exhaust valve 15 is opened together with the rotation of the shaft 22, so that the exhaust timing is slightly advanced.

[0049] shown by R ₁ engine speed at this time in FIGS. In FIG. 11, a straight line a indicates a change in the opening degree of the main exhaust valve 15 for the low-speed range, a straight line b indicates a change in the opening degree of the sub-exhaust valve 18, and a straight line c indicates the change in the opening degree of the main exhaust valve 16 for the high-speed range. Is shown.

The drive block 2 together with the shaft 22
4 and the drive plate 25 also rotate.
4 is in sliding contact with the arc surface 17d of the operation block 17, and the pressing portion 25a of the driving plate 25 is in sliding contact with the arc surface 19e of the sub exhaust valve operation block 19. Therefore, at this time, the high-speed main exhaust valve 16 And auxiliary exhaust valve 1
8 is kept in the fully closed position. The operation block 24
The fan-shaped part 24b of the lower circular surface 1
7e.

That is, the low-speed main exhaust valve 15 is opened before the high-speed main exhaust valve 16 and the sub-exhaust valve 18 are opened.

In this state, the high-speed main exhaust valve 1
Exhaust pressure is applied to the valve 6 and the sub-exhaust valve 18 so that the operation block 17 and the sub-exhaust valve operation block 19 are moved as shown in FIGS.
0, the pressing portions 24a,
Since 25a contacts the arc surfaces 17d and 19e and functions as a stopper, the movement of the high-speed main exhaust valve 16 and the sub-exhaust valve 18 is restricted.

When the shaft 22 further rotates leftward as the engine speed increases, first, the auxiliary exhaust valve 18 starts to open.

That is, as shown in FIG. 10B, the pressing portion 25a of the driving plate 25 abuts on the open side projection 19c of the sub-exhaust valve operation block 19, and the sub-exhaust valve operation block 19 in FIG. It will be biased to the left. At this time, in the drive block 24 that drives the high-speed range main exhaust valve 16, the position of the pressing portion 24a is the position indicated by the two-dot chain line A in FIG. 9A. The rotation angle of the shaft 22 at this time is about 9 ° in the apparatus of the present embodiment. Also,
The position of the tip of the main exhaust valve 15 for the low speed region at this time is shown by a two-dot chain line b in FIG. 2, and the engine speed when the sub exhaust valve 18 starts the opening operation is shown in FIGS.
2 is denoted by R ₂ . The process in which the sub exhaust valve 18 and the low speed range main exhaust valve 15 open and close integrally constitutes the interlocking process according to the present invention.

As described above, the sub exhaust valve operating block 1
9 is activated, the driving block 2
Since the fourth pressing portion 24a is in sliding contact with the arc surface 17d of the operation block 17, the high-speed main exhaust valve 16 is kept in a fully closed state.

When the engine speed increases and the shaft 22 further rotates counterclockwise from the position shown in FIG. 10B, the auxiliary exhaust valve operating block 19 is moved to the position shown in FIG.
At the left side, and the sub exhaust valve 1
8 will open. When the sub exhaust valve 18 is opened,
As shown in FIG. 2, the exhaust timing of the engine is slightly advanced again. Then, a part of the exhaust gas flows to the auxiliary exhaust passage 14.

When the engine speed further increases, the high-speed main exhaust valve 16 starts to open. That is, as shown in FIG. 10B, the pressing portion 24a of the drive block 24 urges the projection 17g of the operation block 17, and the operation block 17 moves to the left in FIG. Then, the high-speed range main exhaust valve 16 is opened by the amount of movement of the operation block 17.

The rotation angle of the shaft 22 at this time is about 51 ° in the apparatus of this embodiment. Incidentally, denoted by R ₃ the engine speed when the high-speed range for main exhaust valve 16 starts opening operation in FIGS. When the high-speed main exhaust valve 16 is opened, the exhaust timing is advanced as shown in FIG.

The engine speed continues to increase, and FIG.
As shown in (c), the auxiliary exhaust valve 18 is fully opened by rotating the shaft 22 until the pressing portion 25a of the driving plate 25 is disengaged from the open side projection 19c of the auxiliary exhaust valve operation block 19. The rotation angle of the shaft 22 at this time is about 56 ° in the apparatus of the present embodiment. The position of the tip of the sub exhaust valve 18 when it is fully opened is the position shown by the solid line in FIG.

When the engine speed further increases after the sub-exhaust valve 18 is fully opened, the upper edge corner of the pressing portion 24a of the drive block 24 becomes a projection 17g of the operation block 17 as shown in FIG. And the high-speed range main exhaust valve 16 is fully opened. At this time, the low speed range main exhaust valve 15 is also fully opened.

When the two main exhaust valves 15 and 16 are fully opened, the exhaust timing is the fastest and the full exhaust passage cross-sectional area is maximized, so that a high output can be easily obtained when the engine is fully opened.

The drive system of the sub-exhaust valve 18 is shown in FIG. 10 (from when the sub-exhaust valve 18 is fully opened to when the low-speed main exhaust valve 15 and the high-speed main exhaust valve 16 are fully opened. It operates as shown in d). That is,
The pressing portion 25a of the drive plate 25 is in sliding contact with the lower edge of the open side projection 19c of the operation block 19, and the auxiliary exhaust valve 18 is kept in a fully open state regardless of the rotation of the shaft 22.

At this time, the main exhaust valve 1 for the low speed range is used.
The positions of the front end of the main exhaust valve 5 and the high speed range main exhaust valve 16 are the positions indicated by the solid lines in FIG. The two main exhaust valves 1
The rotation angle of the shaft 22 when the shafts 5 and 16 are fully opened is about 65 ° in the apparatus of the present embodiment. The engine rotational speed at that time in 11 and 12 indicated by R _4.

When the engine speed decreases from the fully open operation state, as shown in FIG. 11, first, the main exhaust valve 15 for the low speed range and the main exhaust valve 16 for the high speed range begin to close almost simultaneously, and subsequently, the sub exhaust Valve 18 begins to close. When the engine speed further decreases, the high-speed main exhaust valve 16 is fully closed and then the sub exhaust valve 18
Is fully closed, and finally the low-speed range main exhaust valve 15 is fully closed.

When the high-speed main exhaust valve 16 is closed, the pressing portion 24 a of the drive block 24 pushes the side surface of the notch 17 f of the operation block 17. Also,
When the sub-exhaust valve 18 is closed, the pressing portion 25a of the drive plate 25 presses the closing-side projection 19d of the sub-exhaust valve operation block 19.

In the engine 1 configured as described above, the low-speed main exhaust valve 15
Since the number of revolutions R ₁ start opening until the rotational speed R ₃ to start being high speed range for main exhaust valve 16, so that quickened according to the engine speed. And it becomes constant after both main exhaust valves 15 and 16 are fully opened.

Therefore, according to the exhaust valve device of the present invention, the low-speed main exhaust valve 15 which is one of the main exhaust valves is opened before the sub-exhaust valve 18 is opened. The exhaust timing of the engine is controlled by the low speed range main exhaust valve 15 when the engine rises from the low speed range to the middle speed range. Therefore, the exhaust timing control can be accurately performed. In addition, since the main exhaust valves 15, 16 and the sub exhaust valve 18 are driven by one exhaust valve driving mechanism 21, the main exhaust valves 15, 16 and the sub exhaust valve 18 are each driven by a dedicated driving mechanism. Compared with a structure that opens and closes individually, there is no need for an interlocking mechanism for connecting the respective driving devices to interlock the opening and closing timings of the main and sub exhaust valves, and the structure is simplified. With this,
Since the opening / closing timing and opening of each exhaust valve can be determined by one exhaust valve drive mechanism,
Opening and closing control for opening and closing both exhaust valves in association with each other can be easily performed.

In the two-stroke engine equipped with the exhaust valve device according to the present invention, the output characteristics shown by the solid line in FIG. 13 were obtained. In FIG. 13, a broken line indicates a case where no exhaust valve is mounted, a dashed line indicates a case where only one main exhaust valve is mounted, and a two-dot chain line indicates a case where one main exhaust valve and one auxiliary exhaust valve are mounted.

As shown in FIG. 13, it can be seen that when the configuration of the present invention is adopted, high output can be obtained in the low and medium speed ranges.

In this embodiment, the main exhaust valve 15 for the low speed range, the main exhaust valve 16 for the high speed range, and the sub exhaust valve 1
Since the driving of the valve 8 is performed by the rotation of the shaft 22 of the exhaust valve driving mechanism 21, the valve driving mechanism 21 can have a simple structure, and the components can be shared.
The number of parts can be minimized.

[0071]

As described above, the exhaust valve device for a two-stroke engine according to the present invention is disposed at the center of the main exhaust passage, faces the main exhaust port, and changes the amount of protrusion according to the engine speed. And a pair of sliding auxiliary exhaust valves that face the auxiliary exhaust port on the side of the main exhaust port and change the cross-sectional area of the passage, and one exhaust that drives both exhaust valves. A valve driving mechanism, wherein the exhaust valve mechanism has a structure in which an idle stroke in which only the main exhaust valve opens and closes, and an interlocking stroke in which both the exhaust valves open and close integrally, wherein the engine speed is higher than the set speed. When it is smaller, the valves are fully closed, the main exhaust valve is opened when the number of rotations exceeds a set value, and then the sub-exhaust valve is opened when the engine speed increases by a certain value. Since the main exhaust valve opens before the auxiliary exhaust valve opens, the main exhaust valve opens when the engine speed rises from the low speed range to the middle speed range. The exhaust timing of the engine is controlled.

Therefore, even when the engine speed rises from the low speed range to the middle speed range, the exhaust timing control can be performed accurately, and a high output can be obtained over a wide engine speed range. Also, compared to a structure in which the main exhaust valve and sub-exhaust valve are individually opened and closed by a dedicated drive mechanism, an interlocking mechanism that connects the respective drive devices and interlocks the opening and closing timing of both the main and sub-exhaust valves, etc. Unnecessary
The structure becomes simple. At the same time, the opening / closing timing and opening of each exhaust valve can be determined by one exhaust valve driving mechanism, so that opening / closing control for opening and closing the two exhaust valves in association with each other can be easily performed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a two-stroke engine equipped with an exhaust valve device according to the present invention.

FIG. 2 is an enlarged sectional view showing a main exhaust valve driving section of the exhaust valve device according to the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is an enlarged sectional view showing a sub exhaust valve driving section of the exhaust valve device according to the present invention.

FIG. 6 is a sectional view of a main exhaust valve.

FIG. 7 is a view on arrow A in FIG. 1 with a cover removed.

FIG. 8 is an exploded perspective view of an exhaust valve driving mechanism.

9A and 9B are cross-sectional views for explaining the operation of the main exhaust valve for a high-speed range, where FIG. 9A shows a fully closed state, and FIG. c) shows a fully open state.

FIGS. 10A and 10B are cross-sectional views for explaining the operation of the sub-exhaust valve. FIG. 10A shows a fully closed state, FIG. 10B shows a state when opening is started, and FIG. Indicates the fully open state,
FIG. 6D shows a state in which the low-speed main exhaust valve and the high-speed main exhaust valve are fully opened.

FIG. 11 is a graph showing a relationship between an engine speed and a valve stroke amount of the exhaust valve device according to the present invention.

FIG. 12 is a graph showing a change in exhaust timing.

FIG. 13 is a graph showing a relationship between an engine speed and an output of an engine equipped with the exhaust valve device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 engine 13 main exhaust passage 14 auxiliary exhaust passage 15 main exhaust valve for low speed range 16 main exhaust valve for high speed range 17 operating block 18 auxiliary exhaust valve 19 operating block for auxiliary exhaust valve 21 valve drive mechanism 23 drive fork 24 drive block 25 drive Board

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-197629 (JP, A) JP-A-5-26046 (JP, A) JP-A-5-141250 (JP, A) 14529 (JP, U) Patent 3008413 (JP, B2) Patent 3047460 (JP, B2) JP 7-37766 (JP, B2) JP 8-5307 (JP, Y2) (58) Fields investigated (Int) .Cl. ⁷ , DB name) F02B 25/00-25/28

Claims (1)

(57) [Claims] A main exhaust passage provided at a central portion of the main exhaust passage;
A pair of sliding main exhaust valves, each of which has a protruding amount that changes according to the engine speed and changes the exhaust timing, and a sliding main exhaust valve that faces the auxiliary exhaust port on the side of the main exhaust port and changes the cross-sectional area of the passage .
Ride-type auxiliary exhaust valve and both exhaust valves
One exhaust valve driving mechanism, and the exhaust valve
The mechanism includes an idle stroke in which only the main exhaust valve opens and closes,
An interlocking stroke in which both exhaust valves open and close integrally.
When the engine speed is lower than the set speed, the valves are fully closed, and when the engine speed exceeds the set speed, the main exhaust valve is opened, and thereafter, when the engine speed increases by a certain value. Sub exhaust valve for main exhaust
An exhaust valve device for a two-cycle engine, wherein the exhaust valve device is configured to be opened integrally with a valve.